1890.] NATURAL SCIENCES OF PHILADELPHIA. 175 



cannot be regai-ded as having- actually been proposed, while the form 

 itself is manifestly only an attenuated internal cast of C. infundibu- 

 lum. It however exhibits well the characteristic muscular impres- 

 sions. 



This species like C. equllateralis (Hall), with which it is usually 

 associated, occurs in the Burlington limestone and ranges through 

 the Keokuk. Its association with crinoids at Crawfordsville, Indi- 

 ana, has been for the most part with Platycrinus hemisphericus M. 

 & W. ; while at Burlington it adheres to a structurally similar form, 

 Endadoci-inus mUlehrachlutus W. &. Spr. The vault in the first 

 species is very much elevated ai^d the anal opening is situated laterally 

 between, and slightly above, two arm bases. The dorsal cup is orna- 

 mented by numerous conspicuous rounded tubercles. As the grow- 

 ing shell increased in size the pliant apertural margin encountered 

 successively the different nodes, which caused the lip at these points 

 to deflect outward, giving rise to variously shaped prominences on 

 the shell ; when the tubercles were arranged in regular rows there 

 appeared a series of narrow nodular plications. In many cases the 

 gasteropod shell increased in size much faster than the echinoderm 

 and the lip of the shell consequently often encompassed the twopos- 

 terio-lateral arms and not unfrequently also the stem of the crinoid. 

 The result was two large, deep sinuses in the anterior and one simi- 

 lar indentation in the posterior margin of the shell. The effect of 

 the tubercles was to impart a similar sinuous character to the entire 

 margin, hence the lip was always crenated during the latter part of 

 the mollusk's existence. The continual change in the nature of the 

 surface upon which the gasteropod shell rested also interfered with 

 the uniform and regular growth along the apertural margin and the 

 lines of growth are consequently often strongly imbricated. 



Capulus sulcatinus sp. nov. [Plate II, figs. 12a, 12b.] 



Shell of medium size, obliquely subovate, composed of two to two 

 and one-half rather closely coiled or contiguous volution.s, enlarging 

 rapidly toward the aperture. Body Avhorl large and partly free 

 from the small closely coiled spire ; a broad rounded fold extends 

 dorsally along the last whorl. Aperture broadly obovate; margin 

 sharp, undulating, with a wide deeply rounded sinus anteriorly. 

 Surface marked by numerous well defined, nearly parallel longitu- 

 dinal ridges, with broad, rather shallow depressions between ; lines 

 of growth numerous, extremelv sinuous. 



